At the University of Sarajevo, Aleksandar Hemon had an English professor who introduced him to the great works of world literature. And, as time went by, the aspiring young writer would present his own efforts to the great man, who, in turn, was only too happy to nurture his favourite student. Professor Nikola Koljevic taught Hemon just about everything he knew about the world of letters, but his most important lesson - and the most devastating - came later.

When the killing started in the former Yugoslavia, the erudite and admired professor took up the banner of the most bloodthirsty killers.

Koljevic, a Shakespeare specialist, became Radovan Karadzic's smooth-tongued deputy in the Serb Democratic Party and helped run the ethnic-cleansing machine in Bosnia. He spent the war laughing off reports of massacres, smiling as he denied the existence of death camps. And, in a twist Shakespeare himself would have appreciated, Koljevic the man of letters masterminded the bombing of Sarajevo's revered library.

Meanwhile, the student - who had become a refugee in Chicago - looked on in dismay as his former mentor mutated on television into an absurd, chauvinist caricature. Hemon's mother was a Bosnian Serb, but, like her, he had never felt any strong affiliation with the new Serb nationalism. When pressed, he identified himself as Ukrainian - a reference to his father's roots, and exotic enough to be neutral at a time when ethnicity was taking on lethal significance.

"I tried to detect the moment when he [Koljevic] crossed the line," Hemon said. "When did it happen? What were the signs? Should I have known? I re-read things he liked, to see how they were in retrospect. Because I thought if you liked literature and you could quote Shakespeare, you're a good person. At least you couldn't possibly be bad. I learnt that was not true." Thus endeth Koljevic's last lesson. After the war was over, the ex-academic sank deeper into a stupor of alcohol and denial, muttering about the past slights he imagined at the hands of his former academic colleagues, who were by then either dead, emotionally shattered or in exile.

Then, one winter's day in January 1997, the great Koljevic shot himself in the head. In fact, he shot himself twice in the head - a feat that led many to wonder about the official verdict of suicide. But, either way, his days as a Shakespearean authority were over.

Thousands of miles away, his favourite student spent the early years of the war in the utmost misery. Hemon was cut off from his family and friends who were still trapped in Bosnia as the blood began to flow. He had been betrayed by his literary mentor, and by everything he thought literature represented. He was an immigrant with no money, doing odd-jobs in a strange country where he spoke only a tourist phrase-book version of the language.

Fast-forward eight years to present-day O'Hare Airport, Chicago. The big, burly 35-year-old with close-cropped brown hair waiting for my plane to arrive is tipped to be the "new Nabokov" - an outsider who has come to English as a second language and shown us how it should be written. Awards are beginning to fall on him like the first snow in a long winter. His stories have been published in the New Yorker and the latest prestigious collection of Best American Short Stories. This week, his first book will be published in Britain. It is a novella and a collection of stories entitled The Question Of Bruno, and it is generating near-messianic excitement in the publishing world, which fought over the rights in the highest-grossing auction for a literary work last year - £154,000.

The book is a satirical, often surreal, meander through a family's half-remembered, half-imagined history, from the Soviet Gulag to Yugoslavia's woeful past to the life of an exile in millennial Chicago. It is cut up into a series of episodes as different from each other as they are from the rest of current English fiction. Yet, by the end, the book feels like a single work. The stories are connected by common themes - the displacement and mixed allegiances of the outsider - as well as characters and places that seep from one tale to the next, like the irrepressible Hemon dynasty itself. It is semi-autobiographical, in that many of the details are authentic, but they have been rearranged in the interests of literature rather than of history - "a consequence of irresponsible imagination and shameless speculation," as Hemon describes it in one of his stories.

Thus, the doomed Archduke Franz Ferdinand - as he is driven through the streets of Sarajevo on his way to being shot by the assassin Gavrilo Princip - can catch the eye of a smiling accordionist in the crowd who turns out to be Hemon's great-grandfather. The great-grandfather, the accordion and Princip himself all make guest appearances in other stories, as if they were all members and props in Hemon's touring troupe.

The early reactions to The Question Of Bruno have verged on the religious, particularly from Hemon's fellow writers. The remarks of US-based Irish writer Colum McCann typify the general tone. "Anarchic, yet beautifully controlled," he said. "In fact it is difficult to find the proper words with which to praise this book - it creates a sort of awed silence around itself."

Hype and hyperbole are the flesh and blood of publishing, but Picador has indeed stuck its neck out on Hemon's future, putting down an extraordinary amount of cash for a debut volume. And Hemon is drawing praise from people whose whole lives have revolved around the crafting of the English language. So the real question here is: How? Most native-born writers hear English from their days in the womb and spend their lives crafting clauses, polishing paragraphs. Yet they can only dream of the sort of acclaim now piled on Hemon.

Vladimir Nabokov, one of Hemon's literary heroes, had an easy transition by comparison. He grew up in Russia, but in a trilingual household speaking English and French as well as Russian. Nabokov read Browning and Keats as a child, and studied at Cambridge long before he arrived in the US as a refugee. Hemon - or Sasha as everyone calls him - is an engineer's son whose family always spoke Serbo-Croat (Bosnian, as it is now called in post-war Bosnia) and still do in their present exile. His extraordinary accomplishment is really comparable only to the career of Joseph Conrad, who taught himself to write English as a deckhand in the merchant navy. But Hemon even has a few points on the revered Polish novelist. While Conrad was plunged into an English-speaking institution (the navy), Hemon was a mere refugee, one of many in an immigrant-filled city where most get by for years on the sort of tourist pidgin he arrived with.

Hemon's deep, nonchalant Balkan accent is still audible. It rumbles along in its shoulder-shrugging way as he chats about his new life in Chicago. He speaks the language with relish and a sense of appreciation, the same way he writes. However, he points out that his transformation from a struggling Bosnian writer to a successful English author was not some effortless, overnight miracle. First, he had to overcome the illusion, commonplace among refugees, that the war would somehow turn out to be a mere misunderstanding and that he would soon be on a flight home.

Hemon had found himself in the US almost by accident, having been on a government goodwill tour for aspiring foreign writers when the fighting erupted. He had been due to fly home on May 1, 1992, the first day of Sarajevo's four-year siege. He sat dumbfounded in front of CNN on a friend's television set. The next few weeks were a blur of tormented transatlantic calls from public pay phones to his family living in Sarajevo. "I walked around with a pocket full of coins," he said. "The summer of '92 was the worst. People didn't know what to do - how to hide from the snipers. I had no idea what I should do. My father said, 'Stay away.' Then my mother would say something like, 'Oh, the shooting is less than it was yesterday.'" Hemon took his father's advice and stayed in the US, while his parents found their own way out. (They left for Canada in 1993, having slipped out of Sarajevo for Serb-controlled Banja Luka at the beginning of the city's siege.) Their escape lifted some of the personal urgency from Hemon's situation, but it did not diminish the soul-destroying impact of one atrocity after another in a multicultural republic where people used to get along. The nadir of his exile came with the discovery of the horrific Serb prison camps at Omarska and Trnopolje, where Bosnian Muslims were starved, tortured and executed.

"I was devastated by the camps," Hemon said. "I walked around thinking I should get some help. I was even thinking about going to a psychiatrist, but what are they going to say - 'Think positive'? But it should upset you. If it doesn't, then there's something wrong with you." Instead of seeing a shrink, Hemon performed a sort of amputation on himself, severing his ties with the Bosnian language and with his past as a writer. He simply stopped trying to record his thoughts in his mother tongue, notifying his putative employer, Dani magazine in Sarajevo - a feisty, independent journal that documented the war - that he would not be writing any further columns on the grounds that he had nothing relevant to say.

"I couldn't write in Bosnian any more," Hemon said. "Dani called me to ask me to write things, like film reviews. I said I can't write in Bosnian. I was off. Bosnia was off. My Bosnian was pre-war Bosnian." From that moment on, Hemon vowed, he would write exclusively in a language with which he had hitherto had only a colloquial acquaintance. It was a rash act, but Senad Pecanin, Dani's editor and an old Sarajevo friend, was not altogether surprised. "It was a typical thing for Sasha to do. He is a fanatic. A completely impractical person," Pecanin said over the phone, getting quite worked up over the impressive degree of his friend's impracticality. "He is predestined to be either a very successful writer, or a complete disaster. There was no chance of him being an average journalist somewhere."

The chronically unworldly Hemon started keeping a diary written in his tourist's English, and set about expanding his literary vocabulary in the most direct way he could think of - by following in Nabokov's footsteps. "I got myself a copy of Lolita, and I underlined every word I didn't understand, and then I would look them up," he said. "At the beginning it took a very long time, because there were eight or ten underlined words on every page and I looked up the words in the Oxford English Dictionary for Advanced Learners, which has inscriptions and pictures, and some of the words in Lolita weren't in this dictionary."

Hemon soon ventured far beyond Lolita, becoming possessed by what he calls the "library demons". "I read everything all the time," he said, all the while obsessively hoarding his stock of words. He transcribed them on to hundreds of index cards, and if he could not immediately remember a word he had already looked up, he would punish himself with the laborious process of leafing through the weighty dictionary once more. The hoard became a "mental warehouse" of industrial proportions, jammed with a bookish vocabulary that went far beyond the requirements of his employment - which, at that time, consisted of going door to door raising funds for Greenpeace. He would drop words such as "thwart" and "hirsute" into his casual banter, and then wonder why his would-be contributors looked at him as if he were a salesman from Mars. He learnt his next lesson: "Every word has its context. You have to learn the context." Memorising an entire language by rote was an arduous and often dispiriting process, and for a long while, Hemon found himself in the tongue-tied limbo of the hapless exile. "I was between languages for three years. I couldn't write in Bosnian or in English. Whatever I said in English, I was lying, cheating. I was misrepresenting myself."

Eventually, however, Hemon's obsessive dictionary-diving and stockpiling of index cards began to bring results in the deep linguistic recesses of his mind. "I would catch myself using words that I didn't know I knew," he said. "Not only did I begin to think in English, I dreamt in English, and I even remembered in English. I remembered things that happened in Sarajevo as if they happened in English." Hemon had given himself five years to write a publishable story in English, and he ended up achieving his goal in three. In 1995, he wrote an unusual contemplation about espionage, called The Sorge Spy Ring. It contained two narratives in one: on the top of the page was a part-autobiographical account of his own childhood suspicions that his father was a Soviet agent (fictionalised by a dénouement in which the poor man is actually carted off to jail). Below, in the form of a series of historical footnotes, is the true story of Richard Sorge, a German diplomat in Japan who passed on Nazi secrets to Moscow, only to have his warnings of imminent invasion disregarded by Stalin.

Together, the halves constitute a meditation on mixed and complex allegiances - a recurring motif in Hemon's work and life: as a Ukrainian-Serb hybrid in Bosnia when ethnic tensions were at their height eight years ago, and more recently as an immigrant trying to fit in while retaining a distinct identity. "What attracted me was the multiple identity of Sorge," Hemon says. "The idea of 'legend' - a spy's story of his imaginary life. My previous life was my 'legend'. I could say anything about my life, and no one would know it wasn't true. I didn't do it, because I was worried I would get out of control."

Hemon submitted the Sorge story to Reginald Gibbons, writer and teacher at Chicago's Northwestern University who was also the editor of the US literary journal, TriQuarterly. The piece had rough edges, but in Gibbons' eyes it stood out as fresh and innovative. "I liked him very much and I was also interested in his way of working," Gibbons said. "We liked the same writers, such as Bruno Schulz and Danilo Kis. Both are outside the mainstream, and both are writers who wrote not in a straight-ahead way but who tried to capture the unrealistic nature of life.

"Sasha also used these modes outside realism - footnotes, mindgames, telescoping of time - devices that are an attempt to get a hold of a complex and absurd reality . . . I wish there were more American-born writers who would venture out of the realistic box. We seem to need infusions of Sashas." Gibbons also saw Hemon's natural advantage. By coming to the language from outside, he was all the more respectful of its quirks and its peculiar noises, like someone using a car for the first time. "He's had a great ear for the way language is used, and he is very, very gifted," said Gibbons. "It gives him a place to stand which English speakers don't have. Most writers are somewhat lazy and don't listen to what they write. He has a way of hearing English one word at a time."

The remark chimed with something that Hemon said once over the phone. The way he put it was, "In English, I have the linguistic sensibility of a child, and the mind of an adult." Hemon did not expect to be greeted like Nabokov's second coming, and has no aspirations to leave his Edgewater home in the Chicago suburbs, nor give up his weekend football games with Uptown United - a bunch of fellow immigrants from around the globe, who knock the ball about, yelling in mutually unintelligible versions of English.

A diehard Liverpool FC supporter in a country that has never heard of Anfield or the Kop, Hemon says, "It was only after I started playing football and writing that I realised I could in fact live in the United States". But get him on the subject of the current state of English-language fiction and he sounds as arrogant and dismissive as any London literary lord. He does not mean to, and occasionally apologises for giving that impression, but he insists he is simply being straightforward.

However, when he did learn to comprehend English, he found very little to excite him in contemporary writing. When he first hungrily picked up some modern US short stories, he found himself throwing the book across the room. "There was such carelessness about language," he explained. "It was sloppy. And there was that unfortunate tendency towards Hemingway-style minimalism. You remove all the adjectives. I don't believe in that. I believe in Nabokov's way. You pile them up until the object is formed completely."

By now, Hemon was sitting at his favourite local Italian joint and audibly warming to the theme. His second beef was that he initially found very little US or British writing that is about anything. In the comfortable world of the west at the turn of the century, it seemed as though there was nothing to write about except middle-class ennui. "There seemed to be a lack of ambition. There were stories about commuter marriages and mid-life crises. I thought maybe I don't understand this. Maybe it's the language, the culture, but I don't think so. If I'm a good writer, it's because I'm a good reader. I was reading and there was nothing there," he says. "I don't expect them to write about war, but it was so unambitious, as if it was their hobby, as if they didn't need to write stories. I felt I needed to write stories and I couldn't."

Now he can, and has, and is, for the time being, happy with what he's produced. "I wrote this book the way I wanted it," he said at one point during an afternoon-long conversation in Chicago. Hemon believes he is a better writer now in English than he ever was in Bosnian, because of what he has experienced in between: the destruction of his country and life in exile. He checked himself, and pointed out that his problems as a refugee had never been comparable to those who endured Sarajevo's bloody siege, in which 10,000 are thought to have been killed. He is, after all, happily married to an American writer and journalist, and "comfortable" with his mixed identity. "One thing I don't want to do," he declares with a sudden surge of feeling, "is to claim I am the voice of Bosnian suffering."

Yet everything Hemon writes is unmistakably flavoured by Bosnia in all its modern ages - from the assassination of Archduke Ferdinand through the long years of Tito's rule to a golden period of a few brief years between the extinction of communism and the explosion of rabid nationalism, when Sarajevo flowered as an exciting and magnetic cultural centre. The number of Hemon's contemporaries to have settled around the world as successful writers, artists and film-makers is phenomenal. To be creative as a generation, Hemon argued, "you have to have a sense that the old order is not valid any more. I had a sense that the previous generations used it up, used their chance up."

During his spell as cultural editor on Dani, he refused to allow anyone older than 27 to write for the magazine, despite the pleas of his friend and editor, Senad Pecanin. For Pecanin, too, those years - the late 80s, 1990 and 1991 - were a golden era. "Sasha belongs to a good generation of poets, film-makers, and writers right before the war," he said. "At the time, we couldn't imagine a war. Who could attack us, we thought. How stupid."

Many of those who spent much of 1991 partying are still astonished at their own disregard for the menace looming over Bosnia. Hemon explains it this way: "There is a psychological mechanism in human beings which doesn't allow them to imagine their own demise. But the imagination of evil people exceeds the imagination of good people."

The sense of history lurking beneath the present is a key element of the central European experience. It is this history that has condemned the Hemon family to be perpetual outsiders since they arrived in Bosnia from Ukraine. For Sasha, in his story Exchange Of Pleasant Words, the family's rootlessness weighs like a punishment for some past transgression: "Perhaps this is the punishment: we have to live these half-lives of people who cannot forget what they used to be and who are afraid of being addressed in a foreign language, no longer able to utter anything truly meaningful."

It is, Hemon argues, immigrants and outsiders, with their blurred affiliations, who are positioned to write the best prose, because they are one step removed from both a society's language and its everyday reality. It is something he did not fully appreciate when he was Professor Koljevic's favourite student. But Koljevic, while helping to turn a million Bosnians into refugees, also gave Hemon a unique outsider's perspective, and taught him that history counts.

"Before, I didn't see any difference between history and fiction. It was a typical nihilist point of view," he said. "What I later realised was that history came and bumped me on the head, but I should have paid attention all along."

 The Question Of Bruno, by Aleksandar Hemon, is published by Picador on April 21 at £12.99. To order a copy at the special price of £9.99, plus 99p UK p&p, freephone CultureShop on 0800 3166102, or send a cheque to CultureShop, 250 Western Avenue, London W3 6EE. Hemon will be in conversation with Guardian columnist Gary Younge at Waterstone's, 203 Piccadilly, London WC1 at 7pm on April 19; 020-7851 2400 for details.